Biomedical subjects

Frank J Owens

Publications and source records attributed to Frank J Owens.

4 recordsLinked to original sources

PubMed2005

Stability of (C60)2 and epoxide dimers, (C60)2ON, and their anions.

The PM3, AM1, and MINDO3 semiemperical methods are used to calculate the the energy difference between C60ON and C60ON- and the bond dissociation energy necessary to cleave neutral and negatively charged (C60)2 dimers and epoxide dimers, (C60)2ON, to their respective monomers C60, and C60ON/2. The results show that the anions of the dimers are significantly more stable than neutral dimers. This result may explain the higher thermal stability of the observed ferromagnetic phase in photolyzed C60. which has been attributed to epoxide dimers and oligomers. It also provides an explanation for the origin of unpaired electron spin necessary for ferromagnetism.

Journal Article↗

PubMed2005

Confocal micro-Raman observation of nanometer thick oxide layers on metal nanoparticles.

It is shown for the first time that confocal micro-Raman spectroscopy can be used to detect metal oxide nanometer thick layers on metal nanoparticles. The measured frequencies of the observed oxide layers are shifted to lower frequencies and the line widths were asymmetrically broadened compared to Raman spectrum in bulk oxide of the metals. The effects are due to phonon confinement which occurs in materials of nanometer dimensions. Models of phonon confinement are used to estimate the thickness of the oxide layers.

Coated Materials, Biocompatible↗

PubMed2004

Multi-component based cross correlation beat detection in electrocardiogram analysis.

BACKGROUND: The first stage in computerised processing of the electrocardiogram is beat detection. This involves identifying all cardiac cycles and locating the position of the beginning and end of each of the identifiable waveform components. The accuracy at which beat detection is performed has significant impact on the overall classification performance, hence efforts are still being made to improve this process. METHODS: A new beat detection approach is proposed based on the fundamentals of cross correlation and compared with two benchmarking approaches of non-syntactic and cross correlation beat detection. The new approach can be considered to be a multi-component based variant of traditional cross correlation where each of the individual inter-wave components are sought in isolation as opposed to being sought in one complete process. Each of three techniques were compared based on their performance in detecting the P wave, QRS complex and T wave in addition to onset and offset markers for 3000 cardiac cycles. RESULTS: Results indicated that the approach of multi-component based cross correlation exceeded the performance of the two benchmarking techniques by firstly correctly detecting more cardiac cycles and secondly provided the most accurate marker insertion in 7 out of the 8 categories tested. CONCLUSION: The main benefit of the multi-component based cross correlation algorithm is seen to be firstly its ability to successfully detect cardiac cycles and secondly the accurate insertion of the beat markers based on pre-defined values as opposed to performing individual gradient searches for wave onsets and offsets following fiducial point location.

Algorithms↗

PubMed2003

Ferromagnetism above room temperature in bulk and transparent thin films of Mn-doped ZnO.

The search for ferromagnetism above room temperature in dilute magnetic semiconductors has been intense in recent years. We report the first observations of ferromagnetism above room temperature for dilute (<4 at.%) Mn-doped ZnO. The Mn is found to carry an average magnetic moment of 0.16 mu(B) per ion. Our ab initio calculations find a valance state of Mn(2+) and that the magnetic moments are ordered ferromagnetically, consistent with the experimental findings. We have obtained room-temperature ferromagnetic ordering in bulk pellets, in transparent films 2-3 microm thick, and in the powder form of the same material. The unique feature of our sample preparation was the low-temperature processing. When standard high-temperature (T > 700 degrees C) methods were used, samples were found to exhibit clustering and were not ferromagnetic at room temperature. This capability to fabricate ferromagnetic Mn-doped ZnO semiconductors promises new spintronic devices as well as magneto-optic components.

Journal Article↗